Exposure apparatus fob cameras



July l1, 1939- H. F. TNNIES Re. 21,149

EXPOSURE APPARATUS FOR CAMERAS I Original Filed Nov. 19, 1934 2Sheetsv-Shee't l July 11, 1939. H. F. TNMES 1 Re. 21,149

EXPOSURE APPARATUS FOR CAMERAS Original Filed NV. 19, 1934 2Sheets-Sheet 2 Reima! July 111,'193'9 UNITED sTATEs PATENT OFFICE yOriginal No. 2,051,061, dated- Augnst 18, 1936, Se-

rial No. 753,752, November 19, 1934.

Application for reissue October 24, 1938,- Serial No.

'I'his invention relates to exposure apparatus for cameras, and moreparticularly to photoelectric apparatus for facilitating the properexposure of the negative, either by indicating that adjustment of thediaphragm or shutter speed which is appropriate for the light conditionsthen existing or by automatically making the necessary adjustment.

Objects oi the invention are to provide exposure apparatus for cameraswhich is of relatively small size and which may be incorporated in orlocated adjacent the usual lens and-diaphragmassembly with little or noincrease in the size of the camera. An object is to providephotoelectric exposure apparatus for cameras which may serve both as anexposure meter and as an automatic diaphragm,.

the. apparatus preferably being so constructed that the exposure meterportion of the apparatus affords a visual indication as to whether or.not the brightness of the scene to be photographed is in excess of thatcritical value which will permit use of the automatic diaphragm. Afurther object is to provide photoelectric apparatus for incorporationin a. camera adjacent the usual lens anddiaphragm assembly, thephotoelectric apparatus including an electrical measuring vinstrumentactuating a plurality of .diaphragm blades, the measuring instrument andblades being so related that the diaphragm blades can not decrease themaxlmum lens opening unless the measured brightness .o of the scene tobe photographed exceeds that critic al value for which the maximum lensopening and a predetermined snapshot time of exposure are appropriate.Other objects relate to the provision of exposure apparatus including anelecu trical measuring instrument having a single magnet ic circuit anda plurality of moving systems which carry diaphragm blades, the magneticcircuit being of approximately annular form to permit the mounting ofthe electrical instrument in the lens and shutter assembly of a camerawithout substantial increase in the size thereof.

These and other objects and' advantages of the invention will beapparent vfrom the following specification when taken with theaccompanying u drawings in which:

Fig. l is a front elevation of a camera provided with photoelectricexposure Aapparatus embodying the invention;

Fig. 2 is a transverse section through the lens 50 and shutter assemblyas viewed on line 2-2 of Fig. 3, the automatic diaphragm and exposuremeter elements being shown substantially in elevation andthephotosensitive device lbeing shown in central section and turnedthr'ough 90 for the 5|' better illustration ofthe electricalconnections;

`z4 claims. (ol. eis-s4) Figs. 3 and 4 are respectively a top View and alongitudinal section through lens, shutter and exposure apparatus; l

Fig. 5 is a sectional view, similar to Fig. 2, oi

another form of automatic diaphragm construcl tion;

Fig.- 6 is an enlarged fragmentary View of the moving coil and bladeassembly of Fig. 5;

Fig. 'l is a sectional view of another form of the invention;

Fig. 8 is a plan view of a rotary disc calculator;

Figs. 9 and l0 are sectional views of additional embodiments of theinvention;

Fig. 11 is a fragmentary vertical section on line II-IIofFig.l0; l

Fig. l2 is a front elevation of an embodiment of the invention in whichboth the -photosensitive apparatus and the automatic exposure apparatusare incorporated in the lens tube or casing which houses the lenses andshutter `of the camera; and

Fig. 13 is a fragmentary sectional view of a combined automatic andmanually adjustablediaphragm. v

In the drawings, the reference numeral I identiies the casing or lenstube which. supports lenses 2, 2' that are carried by the usual ringmountings 3, 3', the casing having a threaded sleeve l or otherappropriate `means at its inner end for attaching the casing to a camera5. In addition to the lenses, the casing houses appropriate mechanismsuch as shutter 6 and an iris diaphragm I for controlling'the exposureof the negative. The shutter mechanism includes pin 8 which extends tothe exterior of the casing and is adjustable along a scale 9 which isgraduated in the usual 35 manner to indicate the exposure period forsnapshots 'or "instantaneous" exposures, and also the settings for timeand bulb exposures. The diaphragm 'I lis similarly provided withl anindicating arm or pointer IIJ which-is displaceable along a 40 graduatedscale I I to adjust the effective aperture of the lens system. Themechanism for actuating the shutter and diaphragm is positioned, as iscusparatus for indicating, in terms of time or of lens aperture, afactor which affects the `exposure, and also an automatic diaphragmmechanism. This apparatus is energized by the current -developed by aphotocell l2 which may be', and preferably is, of the current-generatingtype,

` the cell being mounted on the camera body behind means, such as amultiple compartment baffle I3 and multiple lens plate I4, lforrestricting the beam of light rays which reaches the photocell toapproximately the image angle of the camera. This type of lightrestricting means is described and claimed in my copending applicationSerial No. 728,573, filed June l, 1934, now Patent No. 2,067,843.

As shown in Figs. 2 and 4, the measuring instrument includes twopermanent magnets I5 of approximately semi-annular form whichYVconstitute a single magnetic circuit with two air gaps in which themoving coils I6, I6' are pivotally mounted. This particular form ofmagnetic field Structure is of small size and makes it possible tolocate the entire assembly within the lens and shutter ycasing I. Thefield magnets surround the axis of the casing and, obviously, themagnets are arranged with their unlike poles in proximity. The movingsystem pointer II having a bent end which moves over an indicator plateI8 within the upper portion I9 of the casing, the pointer end movingalong and adjacent the inner face of the casing to cooperate with ascale 20 on the exterior surface 0f the projecting circular wall I9 ofthe casing.

The scale 20 may be graduated in terms of one of the factors, time ordiaphragm opening, which affect the exposure and, in Fig. 3, a timescale ranging from 16 seconds to 1;@0 second is illusvtrated.

.knob 23 which extends to the exterior of casing I. When the switch isclosed, the moving sys- `tems IB, I6' are displaced in accordancewiththe brightness of the scene toward which the camera and the photocellare directed, and the position of the pointer l1 on the scale 20indicates the appropriate value of one exposure factor when the otherexposure factors have definite preselected values. The illustrated timegraduations 0f scale 20 correspond, for example, to an lassumed filmspeedof 20 Scheiner and an assumed maximum diaphragm opening of f3.5.The corresponding graduations of the shutter speed scale 9 and theYexposure meter scale 20 are preferably in axial alinement. The threeexposure factors are so re1ated-that, if it is preferred to assumedefinite values for film speed 'and exposure time, the scale 20 may begraduated in terms of diaphragm openings. As will be describedhereinafter, this measurement of the scene brilliancy, in terms of onefactor for assumed values of the other factors, may be converted into anequivalent relationship of other `values of the three factors by meansof a computer.

' -The measuring apparatus also includes an automatic diaphragm sinceeach moving system I6, I6' has fixed thereto a sickle-shaped diaphragmblade 2l of light material, such as hard rubber, .a molded syntheticresin or a thin blackened.

sheet of brass or aluminum. In the absence of all current supply to themeasuring apparatus,

I6 carries av the inner semi-circular edges of the diaphragm blades areradially spaced by a substantial distance from the adjacent edges of thelens assembly. The spacing permits a substantial angular displacement ofthe moving systems to take place before the effective diaphragm openingis decreased by the movement of the diaphragm blades into the path ofthelight beainbetween the camera lenses. This delay in the reduction ofthediaphragm opening is necessary for proper operation of an automaticdiaphragm since the apparatus must be designed for one predeterminedVexposure period and, obviously, no decrease in the opening must takeplace until the scene brightness exceeds that critical value whichcorresponds to a full diaphragm opening and the predetermined exposuretime. The illustrated apparatus was designed fora normal snapshotexposure of Q5 second, but it will be apparent that any other value maybe selected for the predetermined normal exposure period. Reverting tothe indicator plate I8, it will be noted that the plate is divided intotwo significant areas I8, Ib, preferably of contrasting color, whichmeet at the 1,455 second graduation on scale 20. .The significance ofthese regions of plate I8 is that, when the camera is directed towards ascene and the pointer Il fails to move out,of the region ISB, theoperator knows that the light is below that critical value which willgive a proper exposure of the film when the shutter is Set for thepredetermined speed of 1,(35 second. Under such conditions, theindicated longer exposure must be used or, for less than the maximumdiaphragm opening, the exposure time must be 4correspondingly increasedbeyond the indicated value.

The diameter of the lens tube I may be some' what reduced or,alternatively, larger diaphragm openings may be had with the samemaximum casing diameter by providing a lost motion conv nection betweenthe'rioving coil system IS and the diaphragm blade 25, Figs. 5 and 6.'Ihis blade is pivotally mounted with respect to the moving coil I-E andhas a slot 26 for receiving the bent end of an arm 2l which is fixed tothe moving coil. The moving coil IE which carries the exposure meterpointer II may therefore return to its normal zero current position butthis outward movement of 'the diaphragm blade 25 and of 'the moving coilI6 and its blade 24 is arrested by spring stops 2li as soon as theblades have moved to clear the maximum lens opening. The blade 25 isreturned to full open position by a coil spring 29 which has its innerend fixed to the moving coil system, the outer end of the blade. Theoperating characteristics of both moving coil systems are substantiallythe same;

and the length of the slot 26 in blade 25 issuch si-hat the initialclosing movement of both blades takes place when the current supply tothe measuring apparatus rises above the critical brightness value whichbrings the pointer I'I into alineynient with the dividing line betweenthe two regions of the indicator plate I 8.

An alternative vcompact arrangement for ob- 'taining a full range ofmovement of the coil I5u and pointer I'Iais shown in Fig. 7. lThe upperportion of the casing Ia is enlarged to permit the blade 24a, of theupper moving system I6, to be withdrawn from the lens opening when themeasured brightness is below the critical value corresponding to thepreselected shutter speed. As in the Fig. 5 construction, the lowermoving vanice system It and diaphragm blade ublengage the stop 23* whenthe blade 24h is clear of the light passage through the lenstube. 'Itwill be noted that the inner edges of the blades'll,` 241 are delined bythree straight lines which form a semihexagonalv recess, the blades thuscooperating to produce a substantially hexagonally shaped openlng which,for optical reasonsis to be preferred when only two blades are employed.Upon increasing vcurrent flow, the moving coil I6u rotates to move blade24n towards the lens, and both coils and their blades are rotated whenthe measured brightness exceeds the value for which a decreaseddiaphragm opening is appropriate.

If the operator wishes to employ a iilm speed and/or a shutter speedwhich differ from the preselected normal values, the computer .shown inFig. 8 may be employed to convert the observed reading of scale 2Ilvinto other equivalent data. The computer includes the stationary disks 3I 32 which are marked in terms of diaphragm openings and film speed, andthe intermediate disk 33 which has a time or shutter speed scale. Theiilm speed value for the type of iilm most commonly used, for example,the value Scheiner, is in line with the maximum lens opening, f3.5,

and the computer is operated by adjusting the disk 33 to bring theobserved time reading, as indicated by the pointer I1 and scale 20,i'ntoalinement with these selected normal values. The illustrated setting ofthe computer is correct for an observed reading of 1/5 Second. Thealined portions of the several scales then indicate vthe proper exposuredata for other iilm speeds and/or smaller diaphragm openings.

' Since this observed reading is more than the selected snapshot settingvof 1/5 second, the operator knows that the automatic shutter blades arenot operative to decrease the maximum aperture. When the brightness ofthe scene is such as to bring the pointer I1 into the region I8h of theindicator plate, the operator may use the normal 1/35 second exposureand the automatic.

diaphragm, or may use any combination of ,stop and shutter speed byfirst moving switchA arm' 2| to open the electrical circuit. By settingthe computer disk 33 to bring the observed time reading, say IAO()second, in line with the corresponding diaphragm opening of f3.5 and 20lm speed, other combinations of the three exposure factors may be readfrom the computer disks.

The measurement of brightness values is not necessary when the camera isprovided with a shutter having a xed exposure period, as is the casewith various types of. motion picture cameras. As shown in Fig. 9, themechanism includes three permanent magnets I5 forming the eldstructure'for the moving coils I6", lid which have diaphragm blades 24|crigidly fixed thereto. Spring stops 28 engage the blades to arrest theopening movement as soon as the blades pass slightly beyond theirmaximum opening positions. The moving coilIGc carries a short pointerI'Ic which is concealed by the casing Ic when the blades are fully open,the pointer moving intol view through the window 30 when the scene is ofsuch brightness that the measuring apparatus produces an appreciableclosln'g movement of the blades. This' particular form of the inventionincludes three overlapping blades but it is to be understood that anydesired number of blades may be used.

As shown in Figs. 10 andll, are carried bycoil systems 35, that are inaxial allnement and pivotally'mounted in the gaps bef desired positions.

l openings.

the blades 34,34'

tween the two sets of pole pieces 36, 38' oi a magnetic field system 31.The direction of current Y iiow through the moving coils is such thatthe coils turn in opposite directions. The general arrangement issimilar to that of Fig. 2 in that the bladesand moving coils are rigidlyconnected and the yblades therefore have a substantial range of idle.movement before the opening is reduced in size. The-magnet is thereforeslotted, as indicated at 33, to permit the necessary outward movement ofthe blades. When the pin and slot construction of Figs. 5 and 6 isemployed, this slotting of the magnet will not be necessary and a singleset of pole pieces may be employed.

It will be noted that a separate coil system -39 is provided fortheexposure meter pointer 4I). This is an alternative for the describedarrangements in which one moving system carries both the pointer and oneof the diaphragm blades.

yAn exceedinglycompact arrangement of the exposure meter and automaticdiaphragm may be had by mounting the photoelectric cell structure on theouter end of the lens tube or casing I, as shown in Fig. 12. .Thecelland lens plate construction described in my copending application makesla comparatively thin assembly which4 need'not increase the overalllength of the lens tube. The cell and lens plate 4I are of annular formand lie between the front lens ring 3 and the outer edge of the casingI;

Whether or not the diaphragm blades are provided for an automaticcontrol of the diaphragm opening, it` is novel, so far as I am aware, toarrange the measuring apparatus of an electrically actuated exposuremeter within a lens tube of the usual design. The advantage of thisdesign is that the moving pointer of the exposure meter travels over ascale that isclosely adjacent the shutter and diaphragm scales. It istherefore to be understood that this invention contemplates a use of theexposure meter elements without the automatic diaphragm blades just as,see Fig. 9, the automatic shutter features may be usually employedwhether or not the exposure meter feaf 'combined by providing means formechanically moving the automatic diaphragm blades into the As shown inFig. 13, the outer ends of the diaphragm blades 24r1 extend into thepath of movement of the lobes 42 which project inwardly from the ring 43that is rotatable in the lens casing Id. The ring 43 has a pointer 44which projects through the casing wall to cooperate with a graduatedscale, 45, of diaphragm The several illustrated forms of the inventionare indicative of the Wide range of latitude in the design andconstruction of the novel exposure apparatus and it is to be understoodthat many,

changes may be made in the design, construction and relative location ofthe various elements without departing from the spirit of my inventionas set forth in the following claims.

I claim: d v

1. Exposure apparatus forphotographic `purposes randy of the typeincluding an electrical measuring instrument adapted to be energized byphotosensitiye means responsive to the brightness of the sceneto bephotographed, characterized by the fact that said apparatus ismountedadjacent the lens of the camera, andk aidinstrument includes indicatingmeans divi ed -into two ranges corresponding to those values of the ISISbrightness of an object to be photographed which lie below and above,respectively, the critical brightness value for which a lm ofpreselected lm'speed will be properly exposed by a preselectedcombination of diaphragm opening and shutter speed.

2. Exposure apparatus as claimed in claim 1, wherein said measuringinstrument includes a plurality of diaphragm blades for controlling theeffective diaphragm opening, said blades restricting the max imumopening only when the bright ness of the object to be photographedexceeds the( said critical value.

3. Exposure apparatus as claimed in claim 1, in combinatipn with anadjustable shutter, an adjustable diaphragm, and means for rendering themeasuring instrument inoperative.

4. Exposure apparatus as claimed in claim 1, wherein the photosensitivemeans is located around the lens at the outer end ofthe lens tube.

5. Exposure apparatus as claimed in claim 1, wherein the electricalinstrument comprises a plurality of moving coil systems and a sing]magnetic circuit therefor.

6. In a diaphragm, the combination with a camera lens, a plurality ofdiaphragm blades for adjusting the eiective lens opening, and measuringapparatus including a plurality of moving coils for actuating saidblades, said measuring apparatus being adapted to be energized byphotosensitive means responsive to the brightness of the object to bephotographed, of means preventing said measuring apparatus from movingSaid diaphragm blades into the path oi the light rays passing throughsaid lens until the' current supply to said measuring apparatus risesabove a.

critical value corresponding toa predetermined brightness appropriatefor a preselected combination of iilmv speed, Speed. V

` '7. A diaphragm as claimed in claim 6, in combination with a pointeractuated by said measuring apparatus anda scale cooperating with saidpointer to measure one exposure factor for a prelens opening and shutterVselected lm speed and preselected value of the other exposure factor.

8. In an automatic diaphragm for a camera lens, an electrical measuringapparatus having a plurality of coil systems, a diaphragm blade carriedby each coil system, means mounting `a coil system-for free pivotalmovement between a no-current position and a maximum-current position inaccordance with the magnitude of the Vcurrent passed through said coilsystem, means mounting the remaining coil systems for pivotal movement,stop means arresting the opening movement of the diaphragm bladescarried. by said remaining coil systems when the saidl blades are clearof the maximum lens opening, a pointer v phragm comprising electricalvmeasuring apparatus adjacent the lens and ,having a plurality of movingcoil'systems, a diaphragm blade carriedby each of said coil systems,- asingle magnetic'eld system oi said lens and cooperating with all of saidcoil systems, and a pointer carried by one of said moving coil systemsand movable over an indicator plate, said measuring apparatus beingadapted to be energized by photosensitive means responsive tothebrightness oi' .the scene to be photographed.

10. The invention as claimed in claim 9, in

combination with manually adjustable diaphragm spondingto ranges ofbrightness above and below that critical brightness value appropriatefor a preselected 'combination` of nlm speed, diaphragm opening and timeof exposure.v

i2. The combination withthe lens of 'a camera,'and a casing housing thelens and adapted to be secured to a camera, of an automatic diaphragmcomprising electrical measuring apparatus adjacent said lens and'adapted to be energized by photosensitive means responsive to thebrightness of the scene to be photographed, said measuring apparatushaving a plurality o! moving coil systems each carrying adiaphragmblade, and a single magnetic field system surrounding the axis of saidlens and cooperating with all 'of said coil systems, and means 4forpreventing operation of said automatic diaphragm.

13. The invention as claimed in claim l2, whereinA said means forpreventing-operation of said automatic diaphragm retains the saiddiaphragm blades in fully opened positions,

14. In an automatic diaphragm, the combination of a casing having spacedlens elements' defining a light passage through the casing,- anelectrical measuring apparatus within said casing having a plurality ofcoils each pivoted on an axis parallel to the axis of the light passageand means forming a single magnetic circuit cooperating with all of saidpivoted coils, and

claim 14, v wherein thereY are two diaphragm blades, and the inner edgeof each blade is defined by three straight lines that form a semiyhexagonal recess in the blade.

16. An automatic diaphragm as claimed in claim 14, wherein each blade isxed toits associated moving coil, the inner edges of said blades beingspaced ,from said light passage 'when said moving coils are notenergized. f

17. yAn automatic diaphragm as claimed i claim 14, in combination withan indicator plate,

a pointer carried by one of said moving coils,r

a lost motion connection between the said coil and its blade, and meansfor 'arresting the opening movement of that blade when it clears thesaid light passage, the said indicator plate being divided into twosigniiicant areas corre-v 15. An automatic diaphragm as claimed in nassociated moving coils and that one or said moving coils carries apointer, said casinghaving a windowopening through which said pointer isvisible substantially only when said moving systems are displaced tosuch extent as to move said diaphragms into said light passage.

19. Photographic apparatus comprising the y combination with a lens tubeand a lens having the mounting ring thereof secured to the front end ofsaidlens tube, of exposure apparatus including a photoelectric cellsupported by said tube and rearwardly oi.' the front end thereof.

20. Photographic apparatus comprising the e combination with ,a lenstube housing the lens of a camera, of exposure apparatus and aphotoelectric cell supported by and at the front end of said tube; saidexposure apparatus including a plurality oi blades adjacent said lensand means energized b y said cell to actuate said blades to restrict theopening through said tube when thebrightness of the object to bephotographed exceeds that critical value for which a preselectedexposure period is appropriate for a preselected iilm speed andthemaximum open-y instrument includes a movable pointer cooper- 22. Anautomatic shutter for a camera, comprising a pair of pivoted diaphragmblades, and electrical measuring apparatus for adjusting said blades,the inner edges of said blades having similar semi-hexagonal recesseswhich cooperate to 5 from a substantially hexagonal opening.

23. Diaphragm apparatus for use with a camera lens, comprising aplurality of diaphragm blades, electrical measuring apparatus includingmoving coils for actuating said blades, and man- 1o ually adjustablemeans to set said blades `mechanically to any desired stop opening.

24. Exposure apparatustor photographic purposes and of the typeincluding an electrical measuring instrument adapted to be energized by15 photosensitive meansrespon'sive to the brightness of the scene to -bephotographed, characterized by the fact that said apparatus is mountedadjacent the lens of the camera; and said ating with indicating meansincluding scale divisions corresponding to preselected increments ofbrightness values and graduated in values of one exposure factor, viz.,diaphragm opening or shutter speed, and means dividing said scale 2sdivisions into two ranges corresponding to those values of brightnesswhich lie above and below, respectively, the critical brightness valuefor which one preselected and ilxed exposure period is appropriate forone preselected and xed tllm 30 speed at the maximum diaphragm openingofthe camera lens.

mms FERDINAND u

